1. Field of the Invention
The present invention relates generally to semiconductor manufacturing processes, and more particularly, to methods and systems for efficiently monitoring and measuring a semiconductor manufacturing process.
2. Description of the Related Art
The semiconductor chip fabrication process requires numerous operations and sub-processes. Examples of such a fabrication operations include etching, chemical mechanical polishing (CMP), deposition, rinsing, drying and other operations. Each of the manufacturing operations must be monitored to make sure that the operation is completed accurately, repeatably and in a timely manner.
By way of example, in CMP, a semiconductor wafer is placed in a holder that pushes a wafer surface against a polishing surface. The polishing surface uses a slurry which consists of chemicals and abrasive materials to cause the polishing. Typically, CMP is used to remove an over burden layer to expose an underlying device layer. If the CMP process is allowed to continue too long then too much overburden material will be removed and the underlying devices can be damaged. Removing too much overburden material can also change the electrical properties of the underlying electrical devices such that their resultant electrical properties are changed beyond an acceptable range. As a result, the circuit formed by the underlying devices would fail to meet the performance goals. In the alternative, if the CMP process is stopped too early, then an insufficient quantity of the overburden material is removed. As a result, the remaining overburden material can cause unintended interconnects between the underlying devices. In CMP, typically some type of an endpoint detector or endpoint monitoring process is used to stop the CMP process in a timely manner.
Other types of manufacturing processes (e.g., etch, rinse, dry, deposition) must also have some sort of subsystem or sub-process capable of monitoring the progress of the respective manufacturing process. This is increasingly important as process control requirements become ever more stringent as device feature sizes become ever smaller and as the level of integration increases. Typically, the monitoring system or sub-process is separate from the manufacturing process. By way of example, in a wet chemical etch manufacturing process, the wet etch process is typically interrupted and the progress is evaluated as follows. The etch process is applied to the semiconductor substrate for an initial period. The semiconductor substrate is then rinsed, dried and removed from the etch process tool to be evaluated using metrology from an appropriate subsystem or sub-process to determine if the wet etch process has reached the desired goal. If the etch process has reached the desired goal (i.e., if the etch process has etched away the desired material) then a subsequent process (e.g., clean, rinse, dry) is applied to the semiconductor substrate.
Alternatively, if the wet etch process has not attained the desired goal (i.e., if the etch process has not removed all of the desired material) then the etch process is applied to the semiconductor substrate again in a rework process. After one or more iterations of the rework process, the wet etch process will remove the desired material from the semiconductor substrate. In the case of a batch processing system, a single semiconductor substrate may be used to verify the rework process required (e.g., to correct process time) before reworking the entire batch of substrates. In the case of a single semiconductor substrate processing system, a similar method could be used before committing an entire lot of substrates for rework wet etch processing.
There are numerous examples of in-situ process monitor methods that are utilized in dry plasma etch processes to provide-thickness loss measurements. These methods often use an interferometer to determine and provide film thickness change information during the etch process. This is problematic when using wet chemical processes because the film of liquid on the surface of the substrate to be measured complicates and can interfere with the measurement.
Additionally, the typical prior art subsystem or sub-process for monitoring the progress of the respective manufacturing process are inherently inefficient because the process itself must be interrupted and restarted multiple times. Starting and stopping the respective semiconductor manufacturing process can also require additional handling of the semiconductor substrate and a more complex overall semiconductor fabrication process. The additional handling and more complex process can introduce additional non-uniformities, defects or mistakes in the semiconductor manufacturing process.
In view of the foregoing, there is a need for a system and method of monitoring and quantifying the semiconductor manufacturing process results within the manufacturing process itself.